I feel like you highlighted the issue yourself.
You expect to get one thing, but then it's suddenly not that thing anymore.
If you pledge because you think the developer is doing a good job as opposed to something more concrete, like a specific sex scene with a character or whatever, it makes it a little different as you don't get that expectation of a specific reward.
There are a lot of games that get cancelled and that sucks, sometimes it's because the developer is unreliable, but sometimes it's because of other reasons. The amount of games and work that get scrapped by big game studios would probably be surprising to a lot of people. The reason you don't hear about it is that because once you announce something then people expect it to be delivered, which is different from how it happens on Patreon.
Although I do get that there a scumbags out there, but not all of us are assholes.
Fair enough, I've been doing weekly updates for I think 78 weeks now so I think I'm in the green on letting people know what I'm doing.
Just thought I'd share my perspective on things.